A technology using a projector, able to display on large screens, for stereoscopically displaying images is being developed and commercialized. In the stereoscopic image display using a projector, a disparity-based method is generally adopted in which Left-eye images and right-eye images are alternately displayed on a screen via the projector. In this method, a viewer is allowed to observe the left-eye image with his or her left eye and observe the right-eye image with the right eye, thereby enabling the viewer to stereoscopically perceiving images using the disparity.
In the disparity-based method, it is necessary to allow the viewer observe respective images corresponding to the left and right eyes. A polarization method is one of the methods of allowing the viewer to observe the respective images corresponding to both eyes.
In the polarization method, the left-eye image and the right-eye image are projected from a projector onto a screen in different polarization states. The viewer is allowed to look at the projected images through polarization glasses with polarization selectivity, whereby the viewer observes the respective images corresponding to the left and right eyes to perceive the images stereoscopically.
As the method for projecting the left-eye image and the right-eye image in different polarization states, a method is proposed in which two sets of projectors are prepared, one projector projects the left-eye image and the other projector projects the right-eye image. In this method, in order to eliminate the inconvenience of preparing two projectors with different polarization states of projected light, it is practiced to use two projectors in an equivalent polarization state, in which the polarization state of projected light from one projector is switched by a polarization element consisting of a reflective mirror. Through this method, it is possible to project a left-eye image and a right-eye image in different polarization states by one projector and the other projector.
In the above-described method of using two projectors, the brightness and color should be matched between the projectors, the position of projection needs to be adjusted and it is time consuming. Moreover, the system cannot be made smaller as two projectors are used, and is inconvenient to use.
Then, PL1 (JP 2004-2059192A) and PL2 (JP H63-018894A) disclose techniques in which one projector projects both the left-eye image and the right-eye image in different polarization states.
In the technique disclosed in PL1, the light emitted from a light source is split into two orthogonal linearly-polarized lights by reflective polarizing plate. Also, in the technique disclosed in PL1, two digital micro-mirror devices (DMDs) are provided on a projector as light modulating elements. The two orthogonal linearly-polarized lights separated by the reflective polarizing plate are each modulated by different DMD. The modulated lights of respective DMDs are combined by a polarized beam splitter, and projected by a projection lens. According to the technique described in PL1, one of the two DMDs performs modulation based on the image signal of the left-eye image, and the other DMD performs modulation based on the image signal of the right-eye image, thereby enabling the left-eye image and the right-eye image to be projected simultaneously in different polarization states from a single projector.
In the technique disclosed in PL2, a liquid-crystal light bulb is alternately driven based on the image signal of the left-eye image and the image signal of the right-eye image. The light emitted from the liquid-crystal light bulb is projected onto a screen through polarization switch element, which consists of a liquid-crystal panel capable of switching its polarization state. In the technique disclosed in PL2, both the left-eye and right eye-images in different polarization states can be projected alternatively in a time division manner from one projector, by switching the polarization state of polarization switch element between driving the liquid-crystal light bulb based on the image signal for left-eye images and driving the liquid-crystal light bulb based on the image signal for right-eye images.